Lifting jack



June 10, 1952 H. SMITH 2,600,276

LIFTING JACK Filed Dec. 16, 1947 '2 SHEETS-SHEET l I7 l I 2/ IO I3 i; I2 $3 24 F 34 25 j x O n I lw in/raz H. SMITH LIFTING JACK June 10, 1952 2 SHEETS-SHEET 2 Filed Dec. 16, 1947 WWW/70F 5 JM/I'f/ Patented June 10, 1952 this, Jacking; Systems Limited, London,

E i and aBri ish o act Application December-16, 1341; Seria'FNQ; 791,955? InGreat-Britain August *1; 19M

7 Claims.

Thisflinventi'on relatesitoc-liitinez i adewsceflal y those ofs;the-.skind :whicho-Vareieitherrportable and. generallystorectinzazmotor-carltool: box: or which: area permanently-attached to .a motor-Bear; this; type beingitthus distinguished-r from, a garageor: trolley typec-oirjacka:

This type of jack has a-.singl-e;-point; ofcontact withi: the .agrounrl; and ,.the;; loose: J' aclr; is, applied understhez motor-carraxleaor" is temporarilya:t-. k tachedatos: the: bumper; or: has a; spigot. for; in? sertion into; an socket. on: the; motor-.car; Whilst thee permanent i jackis; associated with. meansfownormallyvholding;it; in iarr; imperative positiombuinallowing itrtorbemoyed intoqthel-ground en aging positiom The: jack: is: sometimes: a1..- 35 ranged for lifting one side of themotorecar; or onez-wheel,v and; in either; case; difiiculty; is not infrequentlya experiencedqowingto .the instability ofth'ei-motor cariorr thisrsingleipointgi ask support especially? on: a; gradient;v for; example, duesto. 29 thezcamben-iofza road or when-jacking on. a. hill Stiff:chassissandiindependent springing also invol'vesatendency to lift bothifront; wheels:- or both back wheels whencthe:jackzisapplied. With'the interztioniofiliftinggonezwheel only and this increaseszathesi instability of" the; jacked vehicle. The provision of fvery widebase; plates do not offer: a: satisfactory solution: to this. problem; Moreover jacks commonly require. to have a long load bearingamembeir (e. g; thBFSCI'BW of ascrew 30 type jack) the-load. bearing partofwhich in.- creases; in: length: as the load: is lifted: which necessitates a:member of: strong-andheavy cone structionz- According to the presentinvention'. a lifting jacle comprises-a; load engaging: element; an; op:- erative-assembly adapted: to" eiiect: lifting and: lowering of" the said element, and: including a load; bearing; member: at least. as; long; as I the lifting-stroke; two ground engaging strutsa piv- 40 otallyattaehedto theupper end of; the assemblyand: adapted-to-be moved apart at their. lower, ends; and: means for-limiting this movement apa-rt the vload. engaging element being movable only withinthefcompassiof the triangle for ed, by the open struts and the load bearing member being in tensionunder, the load. whereas. the struts are in compression.

Theextensibleelements may consisttota screw and ilnutfhydraulically" operable telescopictubes, atchet elements; or other means.

According to a' preferred constructional form of the invention'the jaclecomprisesa pair of load supporting struts-pivotally att'achediat their upperendsto a load supporting: device and T 2,; adaptedqtosueemor diianaznatr lieir;l9wex-- nds; meaussteelimitzthissmoyementrapar a otatable screw: constituting: load; bear ng; incur-ricer;- mounted at its upperrendson s.ai;d-,.device -;so;as; ts; depend .thereirom hetween; the::struts;; and, ,nut mountech: omit-he; screw and? carrying a 1oad;- en= gaging element; the; nut being; held; a ain t; '7 tati'on duringzthe;liftinettoneraticm whereby the: part: of: the;- screw: which i carries he: oad n: tension is of diminishing length as the loadgais; lifted; whilstuthei struts zwhich carry the loadiin compression: remain of: constant; length; urin operation: and: the: loath enga ing- 1: element, is; in; all DOSitiOIISiV/ithiDTlthQC compass: of the triangle fcrmectjbyv the .openedzlegsn Thesupporting; of the -;1o,ad;always within-the: compassxof: the triangle formed: by; aipairrof pivoted struts; provides a; firnrsupport againfilii tilting and? ate the; same-7 time-1 enables: the: part". of the elongated loadibearingrmemherserr-screw whichicarriessthe? loadanot ;only-to; bein,..tens10n so thatrarmember oiz small dimensionssissuitablebut: assthe: load is: raised this loadv bearing? part becomessshorter'whilst the load: bearing: parts: of 'the strutsaanct other-'partsathatr are; in come- DIBSSiOntdO nota varyrina length;

A constrluctionarfornr of" the invention will; now be described by wayof example wittrrefi erence' to the accompanyingdiagrammatic:drawings-wherein:

Figure is i atvertical :sectional view-:oi a: lifting jack made inaccordance with the invention showing the-struts: spaced apart;

Figure 2. is: a. fragmentary .viewsshowing-rcertainparts inthe -closed ipositions;

Figures; 3; 4 and 'S; aressectional views on the": lines 3C--3, d -d andli -li, respectively:onrrFigure 1; Figure 5 however indicating "only: one strut in closed position;

Figure 6 *isa detail "showing: theloadiengaging member-y Figure. '7 isa view= ofthe lower- 'partoi" amodi- I fied'formof the jack; and

Figure- 8' is a view showing.-

further modifi? cation:

load carrying: device-onblock i ll carries two pivot pins ll 3 I2: which breakinto a hexagonal" recess: I3iformed in the'underside-oftheblock; The block has a central vertical" aperture:

through which passes theupper plain end of a long load bearing member in the formiof aurotatable screw l 6' whichv is-longer than thexlifting stroke This plain end carries a hexagonal nut l lr engageab'le by a brace orvthe like wherebyrthe screwis; rotatable for; e gtending ;-and;; collap ing;-

the jack. This hexagonal nut seats on a ball bearing 18 which in turn seats on the block I0.

Disposed within the recess H3 is a hexagonal collar l9 having recesses engaged by the pivot pins H, [2, which collar carries a downwardly extending tube 20 which is therefore non-rotatable.

Thus the screw and tube and parts carried thereby, together forming a lifting assembly, are suspended on the block Iii. The screw and tube are disposed in the same vertical plane as the struts.

A pin 2! prevents upward displacement of the screw in the block.

The two struts 24, 25, which are longer than the tube, are engaged by the pivot pins H, 12 which are riveted over at their ends so that the struts are pivotally attached to the block W and thus to the lifting assembly.

The struts are of channel section with their closed sides facing outwardly whereby the struts can be brought closely together surrounding the tube. Ground engaging plates 26 are provided at the lower ends of the struts.

Surrounding the tube is a ring 2'! which is con- 2 nected by two links 28, 29 to the struts so that when the struts are closed the links fold within them as shown in Figure 2 and when the struts are opened the links limit the opening movement.

Anut 30 engages the screw and is located within the tube and the nut has a projection 3! extending through a slot 32 along a generatrix of the tube. Seated on the nut and freely surrounding the screw is a collar 34 having a lug ment. The full stroke of this element is within .5:

the compass of the triangle formed by the opened struts whereby great stability is achieved with comparatively short struts.

In the modification shown in Figure l, a link or bar 40 is pivoted to the lower end of the tube and extends in the operative position horizontally equally on both sides of the tube and has each end attached by a pivoted link 4| to the adjacent strut at a short distance from its lower end. The links are of channel form and are narrower than the struts so that these parts can fold together when the jack is not in use with the struts more or less enclosing the tube, lever and links.

In the modification shown in Figure 8, there is no tube such as 28 and in order to prevent rotation of the nut 30 during the lifting operation it has an upstanding dog ii! which engages in a correspondingly shaped slot in the underside of the sleeve 34. In operation, the jack is opened and its feet 26 placed on the ground; the sleeve 34 is raised until the spigot 36 enters the socket provided on the motor-car or other load; the nut is then rotated until the dog 48 engages its slot; and the screw is then rotated to effect lifting.

I claim:

l. A lifting jack comprising a load supporting device, a pair of load supporting struts pivotally attached at their upper ends to said load supporting device, and adapted to be moved apart at their lower ends, means to limit this movement apart, a rotatable screw constituting a load bearing member mounted at its upper end on said device so as to depend therefrom between the struts, a nut mounted on the screw and carrying a load engaging element, and means holding the nut against rotation during the lifting operation, whereby the part of the screw which carries the load in tension is of diminishing length as the load is lifted, while the struts which carry the load in compression remain of constant length during operation and the load engaging element is in all positions within the compass of the angle formed by the opened struts.

2. A lifting jack as claimed in claim 1 wherein a tube is attached at its upper end non-rotatably to the load supporting device and surrounds the screw, and a projection on the nut extends into a vertical slot in the tube through which slot also passes the load engaging member.

3. A lifting jack as claimed in claim 1 wherein the loading engaging member is carried by a sleeve that slidably embraces the screw, the sleeve and nut have engageable parts whereby the nut is prevented from rotating when the load engaging member is engaged in a socket or the like carried by the load.

4. A lifting jack as claimed in claim 1 wherein the struts are of channel shape and of constant cross-section with their closed sides located outwards so that the struts can be brought closely together surrounding the lifting assembly and the means which limit the movement of the struts apart include pivotal members which fold into the channel shaped struts when the latter are brought together.

5. A lifting jack as claimed in claim 1 wherein the load supporting device is in the form of a block, pivot pins attaching the upper ends of the struts to said block, the upper end of said screw passing through the block and supported on a bearing disposed on the block and a hexagonal nut carried by the upper end of said screw for, engagement by an operating tool.

6. A lifting jack comprising a vertically mov-I able load engaging element, a jacking device op eratively connected with said load engaging element to impart a lifting stroke to said element, said jacking device including a load bearing member which supports the load-engaging element and is at least as long as the lifting stroke, a manually operated actuating member for said jacking device and means operatively connected to said actuating member for raising said load engaging element upon operation of the actuating member, two upwardly converging ground engaging struts attached to the upper end of the being movable only within the compass of the triangle formed by the open struts and the ground.

'7. A lifting -jack as claimed in claim 1 wherein the load supporting device is in the form of a hollow block, pivot pins attaching the upper ends of the struts to said block, a tube surrounding said screw, a collar carried by the upper end of the tube and having tangential recesses in the periphery thereof, said collar being positioned within said hollow block and the pivot pins ly- 6 ing in said tangential recesses to retain the col- UNITED STATES PATENTS law within said block. Number Name Date HARRY SMITH- 2ss,32s Webber Nov. 28, M32 REFERENCES CITED 5 2,341,542 Gnme Feb. 15, 1944 The following references are of record in the FOREIGN PATENTS file of this patent: Number Country Date 528,933 Great Britain Nov. 11, 1940 

